Scale (Lepidoptera)
Encyclopedia
The presence of scales
on the wings of Lepidoptera
, comprising moths and butterflies, characterises this order of insects. The name is derived from Ancient Greek
λεπίδος (scale) and πτερόν (wing). The wings of Lepidoptera are minutely scaled, which feature gives the name to this order. Scales also cover the head, parts of the thorax and abdomen as well as parts of the genitalia.
Primitive moths (non-Glossata and Eriocranidae) have 'solid' scales which are imperforate, i.e., they lack a lumen
.
As per Scoble (2005):
The Trichoptera
(caddisflies) which are a sister group of the Lepidoptera have scales, but also possess caudal cerci on the abdomen, a feature absent in the Lepidoptera.
s that give them blacks and browns, but blues, greens, reds and iridescence are usually created not by pigments but the microstructure of the scales. This structural coloration is the result of coherent scattering of light by the photonic crystal
nature of the scales. The scales cling somewhat loosely to the wing and come off easily without harming the butterfly.
, mimicry and warning. Besides providing insulation
, dark patterns on wings provided by dark colour scales would allow sunlight to be absorbed and thus probably have a role to play in thermoregulation.Bright and distinctive colour patterns in butterflies which are distasteful to predators help communicate their aposematism
(toxicity or inedibility) thus preventing a predator from preying on it. In Batesian mimicry
, wing colour patterns help edible Lepidopterans mimic inedible models while in Müllerian mimicry
inedible butterflies resemble each other to reduce the numbers of individuals sampled by predators.
Scales possibly evolved initially for providing insulation. Scales on the thorax and other parts of the body probably contribute to maintaining the high body temperatures required during flight. The 'solid' scales of basal moths are however not as efficient as those of their more advanced relatives as the presence of a lumen adds air layers and increases the insulation value.
Young adults of myrmecophilous
Lepidoptera escape from ant's nests by virtue of the deciduous waxy scales with which they are covered when born. These scales rub off and stick on the ants as they make their way out of the nest after hatching.
Scales also help increase the lift to drag ratio in gliding flight.
Successive close-ups of the scales of a Peacock wing
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
on the wings of Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, comprising moths and butterflies, characterises this order of insects. The name is derived from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
λεπίδος (scale) and πτερόν (wing). The wings of Lepidoptera are minutely scaled, which feature gives the name to this order. Scales also cover the head, parts of the thorax and abdomen as well as parts of the genitalia.
Morphology
The morphology of scales has been studied by Downey & Allyn (1975) and scales have been classified into three groups, namely:- Hair-like or piliform.
- Blade-like or lamellar.
- Other variable forms.
Primitive moths (non-Glossata and Eriocranidae) have 'solid' scales which are imperforate, i.e., they lack a lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
.
As per Scoble (2005):
The Trichoptera
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
(caddisflies) which are a sister group of the Lepidoptera have scales, but also possess caudal cerci on the abdomen, a feature absent in the Lepidoptera.
Structure
Though there is great diversity in scale form, they are structured similarly. The body or 'blade' of a typical scale consists of an upper and lower lamina. The surface of the lower lamina is smooth whereas the structure of the upper lamina is structured and intricate. Scales are attached to the substrate by a stalk or 'pedicel'.Colour
The colouration of butterfly wings is created by the scales which are pigmented with melaninMelanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
s that give them blacks and browns, but blues, greens, reds and iridescence are usually created not by pigments but the microstructure of the scales. This structural coloration is the result of coherent scattering of light by the photonic crystal
Photonic crystal
Photonic crystals are periodic optical nanostructures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons...
nature of the scales. The scales cling somewhat loosely to the wing and come off easily without harming the butterfly.
Function
Scales play an important part in the natural history of Lepidoptera. Scales enable development of vivid or indistinct patterns which help the organism protect itself by concealment and camouflageCamouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
, mimicry and warning. Besides providing insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
, dark patterns on wings provided by dark colour scales would allow sunlight to be absorbed and thus probably have a role to play in thermoregulation.Bright and distinctive colour patterns in butterflies which are distasteful to predators help communicate their aposematism
Aposematism
Aposematism , perhaps most commonly known in the context of warning colouration, describes a family of antipredator adaptations where a warning signal is associated with the unprofitability of a prey item to potential predators...
(toxicity or inedibility) thus preventing a predator from preying on it. In Batesian mimicry
Batesian mimicry
Batesian mimicry is a form of mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator...
, wing colour patterns help edible Lepidopterans mimic inedible models while in Müllerian mimicry
Müllerian mimicry
Müllerian mimicry is a natural phenomenon when two or more harmful species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals...
inedible butterflies resemble each other to reduce the numbers of individuals sampled by predators.
Scales possibly evolved initially for providing insulation. Scales on the thorax and other parts of the body probably contribute to maintaining the high body temperatures required during flight. The 'solid' scales of basal moths are however not as efficient as those of their more advanced relatives as the presence of a lumen adds air layers and increases the insulation value.
Young adults of myrmecophilous
Myrmecophily
Myrmecophily is the term applied to positive interspecies associations between ants and a variety of other organisms such as plants, arthropods, and fungi...
Lepidoptera escape from ant's nests by virtue of the deciduous waxy scales with which they are covered when born. These scales rub off and stick on the ants as they make their way out of the nest after hatching.
Scales also help increase the lift to drag ratio in gliding flight.
Successive close-ups of the scales of a Peacock wing